In recent years, various antibody formulations have been developed, and are actually in use. Many of these formulations are being used in intravenous injections, while there is an increasing demand in clinical practice for development of antibody-containing formulations as self-injectable formulations for subcutaneous injection. Designing antibody-containing formulations for subcutaneous injection makes it necessary to increase the antibody concentration in the administered solution, since a single dose of antibody are very high (about 100 to 200 mg) and the injection volume for subcutaneous injection is generally limited.
Highly-concentrated antibody-containing solutions tend to form highly viscous solutions by themselves due to intermolecular interactions and macromolecular protein characteristics. Furthermore, degradation phenomenon such as aggregation becomes problematic when proteins are stored as highly-concentrated solutions, and thus, this degradation must be prevented. In particular, highly-concentrated antibody-containing solutions tend to form aggregates during freeze-thawing, or when stored in liquid or frozen conditions for a long time (Non-Patent Documents 1 and 2).
Currently, methods for stabilizing highly-concentrated antibody-containing formulations often use highly-concentrated formulations prepared using so-called lyophilizing concentration techniques, in which highly-concentrated antibody-containing formulations are prepared by lyophilizing an antibody solution with a relatively low concentration and redissolving the lyophilized formulation with a smaller volume of water than the volume before lyophilization (Patent Document 1). In this case, however, the increased viscosity of the redissolved formulations is of concern because a cryoprotectant such as sugar must be added to produce the lyophilized formulations.
In that aspect, this problem can be avoided when a liquid formulation is prepared without lyophilization. However, as described above, highly-concentrated antibody-containing liquid formulations tend to form aggregates. Nonetheless, such formulations are highly demanded because antibody-containing liquid formulations are easier to handle than lyophilized formulations, and can be readily formulated into prefilled syringe formulations.
To date, various assessments have been made with the objective of stabilizing highly-concentrated antibody solution formulations (Non-Patent Documents 1 to 4). Arginine is useful as a stabilizing agent to be used for highly-concentrated antibody solution formulations, and it has been reported that the use of arginine can provide highly-concentrated protein or antibody formulations which are stable, have low viscosity, and maintain low turbidity (Patent Document 4). Stable antibody-containing formulations suitable for subcutaneous administration which are characterized in containing arginine and methionine, and have suppressed deamidation and dimer generation during long-term storage are also known (Patent Document 2). On the other hand, there are not many reports on highly-concentrated antibody solution formulations regarding stability to light, and methionine is given as an example that has a photostabilization effect on low-concentration peptide hormones (Patent Document 3).
While the mechanism of the stabilization effect of arginine is not yet known, arginine is widely known as an additive for improving protein refolding induced by heat stress (original text: refolding additive) at low protein concentrations. Based on this, better additives that improve refolding from among arginine analogs were examined, and as a result, argininamide has been reported to be a more effective additive for improving refolding than arginine (Non-Patent Document 5 and Patent Document 5). Amidated amino acids have inhibitory effects against aggregation induced by heat stress, and in such cases, amino groups and amide groups have been reported to be more effective than guanidinium groups (Non-Patent Document 6). Furthermore, arginine ethyl ester is known to have a stabilization effect against heat stress (Patent Document 6).